Pumping system including variable displacement vane pump

ABSTRACT

A variable displacement vane pump has a plurality of vanes slidably fitted in slots formed substantially radially in a rotor. The identical track elements are movably arranged around the rotor to provide a track for the vanes. The positions of the track elements determines the displacement of the pump. Each track element includes a radial inlet passage and a radial outlet passage. The inlet passage of one of the track elements is diametrically opposed from the inlet passage of the other of the track elements and the outlet passage of one of the track elements is diametrically opposed from the outlet passage of the other of the track elements in order to pressure balance the rotor. The track elements are slideably mounted within a frame around which is rotatably disposed a cam actuation ring. Cam members are provided on the cam ring to contact respective can surfaces on the track elements and control the position of the track elements with respect to the rotor. The cam ring is rotated about the frame by means of pistons.

llnited States Patent Cygnor et a1.

14 1 Mar. 21, 1972 Inventors:

Assignee:

Filed:

Appl. No.:

John E. Cygnor, Middletown; Jack G.

Sundberg, Meriden, both of Conn.

Chandler Evans Inc., West Hartford,

Conn.

Apr. 1 4, 1970 01c 21/16, F03c 3/00, F04c 15/04 References Cited UNITEDSTATES PATENTS Balsiger ..418/24 Wilson et a1. ..418/30 X A variabledisplacement vane pump has a plurality of vanes slidably fitted in slotsformed substantially radially in a rotor. The identical track elementsare movably arranged around the rotor to provide a track for the vanes.The positions of the track elements determines the displacement of thepump. Each track element includes a radial inlet passage and a radialoutlet passage. The inlet passage of one of the track elements isdiametrically opposed from the inlet passage of the other of the trackelements and the outlet passage of one of the track elements isdiametrically opposed from the outlet passage of the other of the trackelements in order to pressure balance the rotor. The track elements areslideably mounted within a frame around which is rotatably disposed acam actuation ring. Cam members are provided on the cam ring to contactrespective can surfaces on the track elements and control the positionof the track elements with respect to the rotor. The cam ring is rotatedabout the frame by means of pistons.

ABSTRACT 6 Claims, 11 Drawing Figures Shaw ..41s/30 x Patented March 21,1972 4 Sheets-Sheat 2 FIGJA- INVENTORS JOHN E. CYGNOR JACK G. SUNDBERGBY Pugh! ATTORNEY Patented March 21, 1972 3,65@,642

4 Sheets-Sheet 5 fAOM was fZOl l/ H175? 3% M AZ 70 w/wy/ FZOW F475, 2/0/4 FICELB FIGQ INVENTORS JOHN E. CYGNOR JACK G. SUNPBERG ATTORNEYPatented March 21, 1972 4 Sheets-Sheet 4 26A F|G-6 INVENTORS JOHN E.CYGNOR JACK G. SUNDBERG 255 BY PM MM ATTORNEY PUMPING SYSTEM INCLUDINGVARIABLE DISPLACEMENT VANE PUMP BACKGROUND OF THE INVENTION SUMMARY OFTHE INVENTION The invention provides a variable displacement pump whichis adapted to be incorporated on a fuel control system and a means tocontrol the displacement of the pump which is adapted to be associatedwith a fuel metering system.

The basic pumping structure of the pump includes a rotor having aplurality of perhipherally mounted slidable vanes and a pair ofidentical track elements which envelop the rotor to define a tracksurface for the vanes. The basic pump is of the double-acting variety,in that it has two inlets and two outlets to totally pressure balancethe rotor. A cam actuation ring is rotatable about the track elements tocontrol the positions thereof and hence the displacement of the pump.The actuation ring has two cam members thereupon which are adapted torespectively contact associated cam follower members on the outerportions of the track elements. The angular position of the actuationring determines the position of the track elements and hence thedisplacement of the pump. The displacement of the pump is a functionthen of the position of the actuation ring and this function may bevaried by suitably shaping the cam members on the actuation ring andtrack elements. A servo valve is adapted to receive signals from a fuel7 control which are indicative of the flow demanded ofthe control. Theservo valve in turn controls the position of an actuator which rotatesthe cam actuation ring. The pumping system ofthe invention embodies anuncomplicated design and hence lends itselfto easy manufacture.

Accordingly, it is a primary object of the invention to provide apumping system which incorporates a variable disp|acement vane pump andis adapted to be utilized in conjunction with a fuel control system.

Another object is to provide a pumping system which is capable of beingassociated with the metering system of a fuel control system.

Still another object is to provide a novel and improved pumping systemincorporating a variable displacement vane pump, wherein thedisplacement of the track elements thereof may be determined by thedemands placed upon the fuel control.

These and other objects and advantages will be apparent and understoodfrom the following detailed description when taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectionalelevational view of a pump according to the invention in a maximumdisplacement configuration.

FIG. la is a fragmentary elevational sectional view of the pump of FIG.1 showing the pump in a minimum displacement configuration. I

FIG. 2 is a schematic longitudinal sectional view of the pump of FIG. 1taken along the line 2-2.

FIG. 3 is an interior perspective view of a track element of FIG. 1.

FIG. 4 is an exterior perspective view of a track element of FIG. 1.

FIG. 5 is an elevational exploded view of the track elements of FIG. 1.

FIG. 6 is a perspective view of the frame of FIG. I.

FIG. 7 is an elevational view of a side plate of FIG. 2.

FIGS. 8 and 9 are sectional views taken along the lines 8-8 and 9-9,respectively, of FIG. 7.

FIG. 10 is a perspective view ofa balance piston of FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1, thereis shown a vane pump 10 according to the instant invention in schematicform. With reference to FIG. 1, it is to be noted that the axial lengthof the pump 10 lies in a direction perpendicular to the plane of thepaper. Pump 10 includes a housing 12 having a cavity or recess 14therein, in which the basic elements of the pump are con tained. Aninlet conduit 16 communicates with the cavity 14 for delivering an inputflow of a fluid, such as fuel, thereto. While the device shown in thedrawings is intended to function as a pump and will be described assuch, it will be understood that the design concept could be applied toa motor.

A rotor 18 is splined upon and driven by a drive shaft 20 which extendsthrough the cavity 14, as more clearly shown in FIG. 2. If desired,shaft 20 could also be connected to an impeller pump which in turn wouldsupply inlet fluid to inlet conduit 16, at the charging pressurerequired by the vane pump elements, from a low pressure source such asan uncompressed tank. The charging pressure is defined as the inletpressure required by the vane pump element to insure the vane'spaces arecompletely filled with the pumped liquid. A plurality of vanes 22 areslidably mounted in slots 24 positioned around the periphery of rotor18. The lowerportions of the slots are referenced to discharge pressureby means described hereinafter to radially urge the vanes in an outwarddirection, thereby supplementingthe centrifugal force.

The outer ends or tips of vanes 22 engage a smooth track surface definedby the inner periphery of two identical rigid track elements 26 and 28,the detailed structure of which is I discussed hereinafter. The trackelements 26 and 28 are slideably mounted within a frame structure 30such that they are each movable in directions toward and away from therotor.

Surrounding the frame 30 is a cam structure ring 32 which is rotatablethereabout by actuator assemblies 34 and 36. The actuation ring 32 isprovided with two cam follower members 38 and 40 which respectivelycoact with cam surfaces 42 and 44 disposed on the outer periphery of thetrack elements 26 and 28. The angular position of the actuation ring 32,as controlled by the actuator assemblies 34 and 36, determines thespacing between the track elements 26 and 28, and hence the displacementof the pump. In order to facilitate rotation of the actuation ring 32,balance pistons, respectively designated at 42 and 44, are located inthe housing 12 to contact the respective outer peripheries of the trackelements and urge them inwardly against the pressure forces exerted ontheir inner peripheries. It should be noted at this point that thebalance pistons do not displace the track elements, but merely makerotation of the actuation ring easier, due to the reduced force ofengagement between the cam surfaces 42 and 44 of the track elements andthe respective cam follower members 38 and 40 ofthe actuation ring.

Turning now to FIG. 2, wherein the axial arrangement of the pump I0 isillustrated, it can be seen that at the axial ends of the cavity 14, endplates 46 and 48 are respectively positioned to seal the pump and portdischarge pressure behind the vanes. End plate 46 is fixedly secured tothe housing 12, whereas end plate 48 is mounted for sliding movementupon the shaft 20. A piston assembly 50 functions to pressure load theside plate 48 in the direction of the side plate 46 to seal the pump.Discharge pressure is ported behind a spring loaded piston 52, which isalso slideable upon the shaft 20, to urge the piston 52 into engagementwith the side plate 48.

It will also be noted, with reference to FIG. 2, that the vane 22 iscomprised of two segments, namely 22a and 22b to provide greaterstructural integrity, and to thereby reduce the possibility of vanefailure. These vane segments are not structurally connected to oneanother. With respect to FIG. 2, it will also be noted that the slots 24extend the full axial length of the rotor 18, and that the size of thepockets, formed between the radial inner extremities of the vanes andthe slots, vary as a function of the radial displacement of therespective vanes.

Referring now to FIG. 1, in conjunction with FIGS. 35, wherein thedetailed structure of the track elements 26 and 28 is shown, it shouldbe noted that their inner peripheries 26a and 280 are contoured suchthat portions thereof are circularized, while other portions thereofform cam surfaces which interact with the vanes to cause the vanes tomove radially in and out with respect to the slots. As previouslymentioned, both ofthe track elements are identical structures.

As shown in FIG. 3, track element 26 includes two elongated curvilinearinlet passages 26b and 260 which permit inlet liquid to pass radiallyinward therethrough and fill the pockets formed between the adjacentvanes, the rotor, and surface 26a. These inlet passages extendcompletely through the track element and include recesses or channels inthe track elements at their circumferential extremities. In contrast tothe inlet passages 26b and 260, outlet passages 26d and 26e extend onlypartially through the cam block, 26, but include similar recesses orchannels, and communicate with an axial discharge passage 26f whichextends from one end of the element 26 to the other end thereof. Axialdischarge passage 26f is an internal passage contained wholly within thetrack element 26. The discharge outlets 26g and 2611 of the axialdischarge passage 26fcommunicate with respective discharge conduits inthe housing through mating apertures in the side plates 46 and 48 whichrespectively confront these outlets. The lips of track element 26 definea tongue and groove arrangement comprising tongues 26k and 26L andgrooves 261' and 26j, this being discussed hereinafter. Thecorresponding elements of track element 28 are designated 28a 28L. Itwill be noted from FIGS. 1 and that when the track elements are engagedwith one another, two areas of interdigitation are formed between themating lips.

A specifically defined relationship exists between the circular arcs andcam arcs on the inner surfaces of the track elements and the radialinlet passages and discharge passages; the inlet and discharge areas areoutlined by the solid doubleheaded arrows. In order to facilitate anunderstanding of the invention, the inlet areas and discharge areas forthe track elements 26 and 28, embraced by the solid arrows of FIG. 1,are designated A,, A and A,-', A The spaces between the neighboringinlet areas and discharge areas constitute circular transfer arcs, andare indicated by the dashed double-ended arrows 54, 56, 58 and 60. Thesetransfer arcs are the areas between the inlet and discharge passageswherein the fluid between any two vanes must be sealed to preventcommunication between the inlet passages and discharge passes in thetrack elements. Accordingly, the contour of the inner periphery of thetrack elements in the areas coextensive with the designated transferarcs are circular arcs so that there is no vane displacement while thevanes are traversing these transfer arcs when the track elements occupytheir maximum displacement condition. Stated another way, the trackelements are contoured such that when the track elements occupy theirrespective maximum displacement positions, the transfer arcs are allconcentric with the rotor.

If it is envisioned that the pump will be primarily utilized underconditions which permit the track elements to occupy predeterminedpositions intermediate their maximum displacement and minimumdisplacement positions, then these transfer arcs should be concentricwith the rotor at these predetermined positions for best pumpperformance. For the purposes of describing the instant invention, weare assuming that the prevalent operating condition will be that ofmaximum displacement, and thus it is important, in this maximum pressureload condition, to have the transfer arcs concentric with the rotor.Obviously, if these transfer arcs are concentric with the rotor in themaximum displacement position of the track elements 26 and 28, thenthese arcs will not be exactly concentric when the track elements aredisplaced from their maximum displacement positions. In addition, thelength of each of the transfer arcs is at least equal to or greater thanone vane spacing; that is, equal to or greater than the arc distancefrom a point at the tip of one vane to a corresponding point at the tipof an adjacent vane. The circular contour of the ceiling block in thearea of each transfer arc and the stated minimum arc length of eachtransfer are combine to assure that the inlet and discharge passageswill be isolated from each other so that leakage therebetween isprevented.

The contours of the inner peripheries 26a and 28a in the areas of theinlet and discharge passages (A,, A, and A,. A,,' respectively) are allcam surfaces, and the distance between these surfaces and the outerperiphery of the rotor progressively changes along the arcs of theseareas. Therefore, there is a net vane displacement as these inlet anddischarge areas are traversed by the vanes, and this displacementresults in a fluid discharge as each of the discharge areas is traversedand a fluid intake as each of the inlet areas is traversed.

At this point, it would be profitable to describe the operation of thepump as the vanes traverse the vane track or guide defined by the innerperipheries or surfaces 260 and 28a of the track elements. Assuming thatthe track elements occupy their maximum displacement positions, and thatthe shaft 20 and the rotor 18 are rotating counterclockwise, theanalysis begins with the upper edge of the inlet area A, oftrack element26 at itsjuncture with transfer arc 54. Bearing in mind that the contourof track element 26 in the area of transfer are 54 is a circular arcconcentric with the rotor, it can be seen that the contour ofthe innersurface 26a oftrack element 26 changes from a circular arc to a camsurface at the point of juncture of arrow 54 and the inlet area A,. Thecontour of the inner periphery of track element 26 in the area A,recedes from the rotor 18 as the inlet area A,- is traversed in acounterclockwise direction so that the separation between the rotor 18and the inner periphery 26a of the track element 26 in the inlet area A,increases at successive counterclockwise stations along the inlet areaA,. Assuming that the outer ends of the vanes 22 are caused to remain incontact with the inner peripheries of the respective ceiling blocks,either by centrifugal force or fluid pressure under the vanes, each vaneis thereby caused to move within its slot in a radially outward fashionfrom the surface of the rotor 18 as the vane traverses the are definedby the inlet area A and each successive vane in turn in acounterclockwise direction will be in a more extended position than thevane immediately trailing it in the direction of rotation. There is thusa net increase in the volume defined between the side plates 46 and 48and any two vanes as the vanes move in a counterclockwise directionalong the arc of the inlet area A,. Thus, a fluid, such as fuel, madeavailable to the inlet passages 26b and 260 via inlet conduit 16 and theopenings in the frame 30, enters into the intervane volume as the vanestraverse the arc of the inlet area A,. As each vane reaches the end ofthe arc of inlet area A,, it enters into the area defined as transferare 60. Bearing in mind that the inner periphery of the track elementencompassed by transfer are 60 is a circular are concentric with therotor surface in the maximum displacement positions of the trackelements s 26 and 28 (FIG. 1), and that the arc length of transfer arc60 is at least equal to or greater than one vane spacing, the volumebetween any two vanes (sometimes referred to as the intervane volume)remains constant in traversing are 60, and the volume is at leastmomentarily sealed from the inlet area A, and the discharge area A,,.Because of the fact that the contour of the inner periphery of the trackelement is a circular arc along transfer arc 60, there is no attempt tocompress the fluid contained in the volume between two successive vaneswhen traversing the are 60. Thus, a serious overloading of the pump isavoided by this design. It should also be noted that there is no inwardor outward movement of the vanes as they traverse are 60 and, therefore,sliding friction loads between the vanes and their respective slots areavoided as the vanes traverse are 60.

The vanes now enter into the arc defined by outlet area A The innerperiphery of the track element 28 in the discharge area A is a camcontour which progressively decreases the distance between the innerperiphery 28a of the track element 28 and the surface of the rotor 18with reference to a counterclockwise direction. Since the separationbetween the surface 28a and the rotor 18 progressively decreases as thedischarge area is traversed in a counterclockwise direction, each vaneis cammed inwardly in its slot during traversal of outlet area AAssuming for example that the discharge outlets 28g and 28h of the axialdischarge passage 28f are in fluid communication with a load (such as afuel nozzle or a pressurizing valve), the fluid in an intervane volumewill become pressurized as the fluid in the intervane volume traversestransfer are 60 and becomes exposed to the discharge area A that is,fluidly communicates with the radial discharge passages 28d and 28e. Thepressurized fluid then coming within the arc of the discharge area Awill then be forced out through the discharge outlets 28g and 28h viaradial discharge passages 28d and 282, and axial discharge passage 28f,as a result of the vanes being displaced inwardly with respect to theirslots by the camming action of the cam contour of surface 28a along thearc of discharge area A,,. This inward displacement of the vanesresults, of course, in a reduced volume between any two vanes as thevanes move counterclockwise along the arc of discharge area A and thefluid is thereby forced to move from this reduced volume out of radialdischarge passages 28d and 28e.

It will be appreciated thatthe pumping capacity of the pump of FIG. 1 isa direct function of the displacement of the vanes as the vanes traversedischarge area A and are cammed inwardly therewithin. After traversingthe arc of discharge area A each vane then enters into transfer are 58,the inner surface of the track element 28 within transfer are 58 issimilar to transfer are 60 in that it is a circular arc, whereby thereis no inward or outward displacement of the vanes as they traverse are58. The are width of are 58 is also at least equal to or greater thanone vane spacing, so that the in tervane space between any twosuccessive vanes is at least momentarily sealed as the vanes advancefrom the end of discharge A toward the beginning of inlet area A,'.Thus, leakage around the rotor between discharge area A and inlet areaA, is thereby avoided.

The contour of the inner periphery 28a of track element 28 in thevicinity of inlet area A," is, ofcourse, the same as that in thevicinity of inlet area A,; that is, the contour of the inner periphery28a of track element 28 within the arc of inlet area A, recedes fromrotor 18 as the inlet area A, is traversed in a counterclockwisedirection. Thus, the inner periphery of track element 28 within the arcof inlet area A, is a cam surface which results in an increasingintervane volume and a consequential drawing of fluid into theincreasing intervane volume as the vanes traverse this inlet area in acounterclockwise direction.

Immediately after leaving inlet area A;', each vane passes throughanother transfer arc 56 which, like transfer arcs 60 and 58, is of acircular contour and is at least equal to or greater than one vanespacing so that there is no vane displacement while traversing thetransfer arc, and so that the intervene spacing between any two vanes isat least momentarily sealed from both inlet area A,-' and outlet areaA,, to prevent leakage therebetween. After traversing transfer arc 56,each vane then enters into the arc defined by discharge area A,,. Thecontour of the inner surface 26a of track element 26 within the arc ofdischarge area A as is the case with discharge area A 40 as is the casewith discharge area A is a cam surface which advances toward rotor 18 asthe arc is traversed in a counterclockwise direction Thus, separationbetween the inner surface 26a of the track element 26 and rotor 18diminishes as discharge area A is traversed in a counterclockwisedirection, thereby resulting in an inward displacement of each vane inits slot as the vane traverses discharge area A,,.

In a manner similar to that previously described with reference todischarge area A the fluid in an intervane volume traversing transferare 56 becomes pressurized as the intervane volume comes under theinfluence ofdischarge area A,,. The pressurized fluid in the intervanevolume is then forced out of the space between the rotor and the innerperiphery of the track element in the discharge area as the vanes areinwardly displaced in their slots, and the intervane volume decreasesduring the traversal of this area. After passing through the arc ofdischarge area A,,, each vane enters into yet another transfer arc 54.

The contour of the inner periphery of the track element 26 encompassedby transfer are 54 is a circular arc having a width at least equal to orgreater than one vane spacing. Thus, as previously described withrespect to transfer arcs 60, 58 and 56, transfer arc 54 is an areathrough which the vanes undergo zero radial displacement during movementtherein, when the track elements occupy their respective maximumdisplacement positions as shown in FIG. 1. This arc 54 comprises atleast a momentary seal for each intervane volume between the dischargearea A and the inlet area A,.

It will be appreciated from the foregoing that the described mode ofoperation relates to a double-acting pump; that is, a pump with twoinlet areas and two outlet areas. It will also be apprehended that thetwo inlet areas are diametrically opposed, and that the two outlet areasare similarly diametrically opposed, thereby pressure balancing therotor. It will also be appreciated that for the illustrated pump design,the durability of the pump is enhanced at maximum pressure loads becausethe transfer arcs 54, 56, 58 and 60 are concentric with the rotor.Further, the foregoing illustrative description of the operation of thepump, as rotor 18 moves in a counterclockwise direction, has beendirected to an analysis as a vane or a pair of vanes traverses the vanetrack defined by the inner peripheries 26a and 28a of the track elements26 and 28, respectively. It will, of course, be understood that theactions previously described in connection with the inlet and outletareas and the transfer arcs occur simultaneously with respect to vanesor sets of vanes around the circumference of the rotor so that theseveral described inlet discharge and seal transfer actions are alloccurring simultaneously. It will also be understood that each inletarea in reality encompasses two passages, as depicted in FIGS. 3 and 4.Thus, the inlet area A, embodies radial inlet passages 26b and 260, andthe outlet area A embodies radial outlet passages 26d, 26e.

Turning again briefly to FIG. 2, it can be seen that the outlets 28g and28h of the axial discharge passage 28f respectively discharge fluid intodischarge conduits 62 and 64 via appropriate discharge apertures in sideplates 48 and 46. The interrelationship between the side plates 46 and48 and the track elements is more fully discussed hereinafter.

The smooth contour transition along the inner peripheries of the trackelements 26 and 28 result in minimum vane dynamics problems for alldisplacement conditions and notably that ofmaximum displacement. As willalso be discussed hereinafter, in connection with the bridge structureor area of interdigitation between the track elements 26 and 28, thevane track contour defined by the inner peripheries 26a and 28a isformed to provide smooth transition and preserve minimal vane dynamics,irrespective of the relative position of the track elements betweentheir maximum displacement and minimum displacement positions.

Turning now to FIG. 1a, the pump is now shown with the track elementsmoved apart to a position wherein the pistons are at their outer limitsof travel, and the pump is at a minimum displacement configuration. Ifdesired, movement ofjust one of the track elements could be used tounload the pump, and this would permit the elimination of one of the camsurfaces 38 and 40 on the actuation ring 32 and one of the pistons 34and 36. It should be understood that with the arrangement illustrated inFIGS. 1, 1a and 2, the track elements could be caused to assume anyposition between the loaded position of FIG. 1 and the unloaded positionof FIG. la for partial loading. While the means shown which moves thetrack elements is a cam ring incorporating two cam follower membersthereupon, it will be appreciated that any actuation structure having acam surface thereon could be employed to displace the track elements,but that the utilization of two diametrically opposed cam followermembers prevents the actuation ring 32 from bearing against the frameand engendering friction which would be detrimental to the control ofthe pump.

As can be clearly seen in FIGS. 3-5, the track element 26 includes a liphaving two grooves intermediate the axial ends thereof, these groovesbeing designated 261' and 26j. Also included in the track element 26,across from the grooves 26i and 26] on the other lip, are two tongues26k and 26L. The grooves and the tongue structures in track element 28are denoted 281', 28j, 28k and 28L. At this point, it should be notedthat the tongue 28k and 28L are adapted to slidingly fit in the grooves261' and 26], and that the tongues 26k and 26L are adapted to slidinglyfit in the grooves 28f and 28j. It is also important to note that theinner periphery of the track elements in the area ofthe grooves isarcuate and constitutes part of the inlet cam surface. The tongues,however, are flat on their inner peripheries and thus the innerperipheries or surfaces of each tongue define a flat plane or surface.The flat plane ofthe inner surface ofeach tongue is arranged to betangent to the inner periphery of the track element with which it isassociated. Stated another way, the inner surface of the tongues istangent to the inner periphery of their respective associated trackelements at the lines ofjuncture between the tongues and the trackelements. Referring to FIG. 5, wherein the track elements 26 and 28 areshown spaced apart from one another in an exploded view, which, ofcourse, is not the case in the actual pump, it can be observed that theinner surface 66 of tongue 28L is tangent to the contour of the theinner periphery 2a of the track element 28 at its line ofjuncture 68.Similarly, the inner surface 70 of tongue 26L is tangent to the innerperiphery 26a of track element 26 at its line ofjuncture The grooves 26jand 28] shown by the dashed lines in FIG. 5 are adapted to receive thetongues 28L and 26L. With reference to FIG. 5 and FIG. 3, it will benoted that the grooves 26j and mating tongues 28j form part of inletareas A and A," by virtue of the recesses at the extremity of the inletpassages adjacent the grooves and the recesses at the tips of thetongues and that during clockwise rotation of the rotor 18, the tip of avane traveling on the inner periphery 26a of track element 26 will passover the groove and then contact the inner surface 66 of tongue 28L whenthe pump is in a minimum displacement condition in which the trackelements are spread apart, as shown in FIG. la. Similarly, a vanepassing over the groove 28j will contact the surface 70 in the FIG. laconfiguration. The planar inner surfaces 66 and 70 of the tongues 26kand 26L are machined so that the edge of each tongue will not protrudefrom the periphery 26a in the maximum displacement position to precludea vane tip from engaging the tip ofa tongue and rendering the pumpinoperative. Alternatively, the outer surfaces of the track elements maybe machined to insure this arrangement. It is important to note that thevane always proceeds from a groove to a tongue, as can be seen fromFIGS. 1, 1a, and 35, when the track elements are in their maximumdisplacement position, the tips of the tongues of one track element abutthe bottoms of the grooves of the other track element and the vanes passessentially directly from one inner periphery to another innerperiphery; that is, from inner periphery 26a directly to inner periphery28a, and subsequently from inner periphery 28a to inner periphery 26a.However, except in that one condition of maximum displacement, whereinthe tongues of one track element are firmly received in the grooves ofanother track element, the transition of the vanes from the innersurface of one track element to the inner surface of another trackelement is guided by the inner flat surface on the tongue of the othertrack element.

The design of this pump, with its two identical vane track elements,lends itself to fabrication. To insure the proper relationship betweenthe internal contours of the two vane track elements required for apump, the final sizing and finishing operations are performed on thepair of vane track elements when they are fixed in the zero displacementposition. In this position, the complete contour is exposed. The twovane track elements are then considered matched pairs.

Referring now to FIG. 6, there is shown a perspective view of the frame30. The frame 30 comprises a pair ofthick walls and 82 which have planarinner surfaces 84 and 86 which are parallel to one another. The innersurfaces 84 and 86 of the frame 30 are adapted to abut the parallelsides (the vertical outer sides of FIG. 5) of the track elements toguide the track element in their movement between minimum and maximumdisplacement positions. With references to FIGS. 4 and 5, it can be seenthat the track element 26 comprises a generally flat outer surface 26swhich is contacted the balance piston assembly 42'. The balance pistonassembly 44' is, of course, adapted to bear against the correspondingsurface on track element 28.

As best shown in FIG. 10, the balance piston assembly 42' comprises apiston 90 and pair of spaced legs 92 and 94. The slots 96, 98 in theframe are adapted to slidingly receive the respective legs 92 and 94.The balance piston assembly 44' is identical to balance piston assembly42', and the depending legs thereof project through slots 100 and 102 ofthe frame 30 to engage surface 283 of the track element 28. Thedepending legs of the balance piston assemblies straddle the rotatableactuation ring 32 which is disposed intermediate the slots 96 and 98.Between the slots 96 and 98 in another slot 104 which develops into alarger opening 106. Similarly, on the diametrically opposed side of theframe 30, slot 108 is similarly disposed between slots 100 and 102, andsimilarly develops into a larger opening 110. All of the slots andopenings allow fluid to pass radially through the frame to the inletpassages in the track elements.

Although in the schematic view of FIG. 1 the cam member 38 is shown tothe left of depending leg 94, for the sake of clarity it will beunderstood that cam member 38 protrudes through slot 104 and is guidedby the sides thereof during rotation ofthe actuation ring 32. Similarly,cam member 40 on at:- tuation ring 32 protrudes through slot 108 and isguided by the sides thereof during rotation of the actuation ring. Itwill further be understood from FIGS. 3 through 6 and 10 that thedepending legs on the balance pistons not only straddle the actuationring, but also straddle the cam surfaces on the track elements. Theframe 30 also include two holes 112 and 114, and a similar pair ofaxially aligned holes on the end of the frame which is not shown. Thepurpose of these holes is to mount the sides plates 48 and 46.

Turning now to FIGS. 7 through 9, wherein the construction of the twoidentical side plates is shown, each side plate includes a centrallydisposed opening through which the splined shaft 20 of FIG. 2 isreceived. Spaced from the opening 20 are two elongated dischargeapertures 122 and 124 which are shaped as the discharge outlets (26g,26h, 28g, 28h) ofthe track elements 26 and 28 and are disposed againstthese discharge outlets in a mating relationship. As shown in FIG. 2,the discharge aperture 124 receives from the axial discharge passage28fof track element 28 via the discharge outlet 2811. Still referring toFIG. 2, flow from the discharge aperture 124 of side plate 46 proceedsthrough discharge conduit 64. Discharge conduits 62 and 64 merge to forma single discharge conduit 65. Similarly, flow from discharge outlet 28gproceeds to discharge conduit 62 via discharge aperture 124 of sideplate 48. The respective discharge apertures 122 of the side plates 48and 46 similarly receive output flow from axial discharge passage 26fand deliver the output flow to another pair of discharge conduits (notshown) which merge as discharge conduits 62 and 64 into a single conduitwhich joins conduit 65 in the housing 12. Spaced from the boundaries ofthe opening 120 is a circular recess 126 which communicates withdischarge pressure via recesses 128 and 130. The recesses 128 and 130serve to fluidly interconnected the recess 126 with the dischargeapertures 122 and 124 respectively, thereby maintaining high pressure inrecess 126. As can be seen in FIG. 2, the respective recesses 126 oftheside plates 46 and 48 port discharge pressure to the underside of thevanes via the respective vane slots to keep the vanes in firm contactwith the track surface defined by the track elements. In order toprevent this discharge pressure in recess 126 from separating the sideplates from the axial end of the pump, two auxiliary recesses 132 and134 extend across the side plate. Thus, if a large pressure develops inrecess 126, pressure will not be produced near the edge of the plate(which could possibly lift the plate off the pump), but instead flowwill proceed from recess 126 tothe recesses 132 and 134 which arereferenced to the inlet pressure of cavity 14. Thus, only the area ofthe side plate encompassed by the recesses 132 and 134 will be exposedto high pressure, should the discharge pressure in recess 126 rise to aprohibitive value.

Lugs 136 and 138 are secured to the side plate and project axiallytherefrom and are adapted to be received in the holes 112 and 114respectively of the frame 30 and the corresponding set of holes on theside of the frame not shown. As previously mentioned, the side platesare urged into firm engagement with the axial ends of the pump by meansof piston 52, and thus the auxiliary recesses 132 and 134 merely providean extra margin of safety.

The control system for the pump is shown schematically in FIG. 1. itshould be noted at the outset that although the elements which form thecontrol system are shown located in the housing, they could, if desired,be located in separate housings and interconnected by suitable conduits.The basic elements of the control system for the illustrated pump are aservo valve, generally designated at 140, which forms the heart of thecontrol system, a wash flow filter 142, which filters the output flowfor certain control functions, and a needle type pressure relief pilotvalve 144, which prevents the output pressure from reaching apredetermined value by controlling, leakage across the side plate 48.

Referring again briefly to P16. 2, it can be seen that dischargeconduits 62 and 64 join to form a single conduit 65 which directs outputflow to the wash flow filter 142. It will be remembered that the pumpalso includes two other discharge conduits (not shown) which merge intoa single discharge conduit, these conduits communicating with the axialdischarge passage 26f of the track element 28 via the respectivedischarge apertures 122 of the side plates 46 and 48. This singledischarge conduit joins with the discharge conduit 65 upstream of thewash flow filter 142. Thus, the wash flow filter 142 receives the outputflow from four discharge conduits in the pump housing, two of which are62 and 64.

Flow passes axially through the wash flow filter 142, which is agenerally cylindrical structure, to a main discharge conduit 146. Maindischarge conduit 146 could be connected to the inlet ofa fuel controlor another type of control depending on the application for which thepump is selected. Fluid, which enters the filter and does not passtherefrom to main discharge conduit 146, passes radially through thefilter element 148 into an annular chamber 150. Two conduits 152 and 154communicate with this annular chamber forcarrying filtered output flowto various elements in the control system. Conduit 152 carries filteredoutput flow to the outer face of balance piston 90, and conduit 154carries output flow to the outer face of the balance piston assembly 44via a secondary conduit 156. Thus, pump discharge pressure urges thelegs of the balance pistons against the tract elements to urge the trackelements in the direction of the rotor. Of course, this pressure willnot physically move the track elements, but will merely render it easierfor the actuation ring to control the displacement ofthe pump aspreviously described.

A branch conduit 158 communicates with conduit 152 to carry filtereddischarge flow to pressure relief valve 144 and the outer face piston52, the discharge flow being communicated to the outer face of thepiston 52 via conduit 160, which is also shown in FIG. 2. Conduit 158embodies an orifice 162 which permits the pressure, communicated to theouter face of piston 52, to be slightly below that of the discharge. Thepilot operated relief valve 12 is a spring biased needle valve whichincludes a piston 162 which is urged downwardly within its cylinder by acompression spring 164. On the lower face of piston 162 is secured aneedlelike shaft 166 which controls the flow from conduit 158 to areturn conduit 168 which communicates with the inlet conduit 16.Conduits 170 and 172 respectively interconnect conduits 158 and 168 withthe cylinder of relief valve 12 at respective locations below the lowerface of piston 162 and above the upper face of piston 162. Thus, if adischarge pressure should exceed a predetermined value, the forceexerted upon the piston by the pressure communicated via conduit 158 andconduit 170 will overcome the bias provided by the spring 164 and theinlet pressure acting on the upper face of the piston 162, therebycausing the piston 162 to rise vertically in its housing and permittingfluid communication between conduits 158 and 168. The orifice developedbetween the needle valve and its seat operates in conjunction withorifice 162 to schedule the pressure to the piston 62 (via conduit 160)and thereby achieve a force balance across the side plate 48 to permitit to float, this floating maintaining the maximum pressure differentialby a controlled internal leakage across the side plate 48.

The servo valve 140 is the heart of the control system in that it is themechanism by which the actuation ring is controlled, and hence controlsthe displacement of the pump. Each of the actuator piston assemblies 34and 36 includes a piston 174 which is slideably mounted within asuitable cylindrical cavity and is attached to a shaft 176. The shafts176 are pivotally connected to the links 178 which in turn are pivotallyconnected to the actuation ring 32 at diametrically opposed locations.The diametrically opposed locations on the actuation ring, to which theshafts 176 are respectively connected, insure that the actuation ring 32will not bear against the frame 30 when rotated, but will only be guidedthereby. The arrangement contributes to maintaining friction between theactuation ring 32 and the frame 30 at a minimum value. The inner andouter faces 180 and 182 respectively of the piston 174 are exposed topressures which create an axial force imbalance on the piston 174 todisplace the piston or hold it in a fixed position. The inner faces ofthe pistons are in communication with an interconnecting conduit 184which is connected to the servo valve 140. The outer faces of thepistons ofthe actuator piston assemblies are interconnected in a likemanner by interconnecting conduit 186. The interconnecting conduits 184and 186 are fluidly connected to the servo valve, as is describedhereinafter.

The servo valve per se comprises a spool having four lands 188, 190, 192and 194, the spool being slideably disposed within a bore 196. The bore196 comprises two main ports 198 and 200 which respectively communicatewith the interconnecting conduits 184 and 186. Bore 196 also includessecondary ports 202, 204, 206 and 208. The ports 202 and 206 communicatewith this annular inlet area via conduit 210 and branch conduits 212 and214. Port 204 communicates with discharge pressure via conduit 154.Normally, the spool will be disposed within the bore 196 such that landcovers port 198 and land 200 covers port 208. In this condition, theother ports 202, 204 and 206 will communicate with the annular spacesdefined between the lands of the spool. Connected to the left end of thespool is a bellow 216 which is housed within a cavity 218 whichcomprises an annular abutment 220 to which the bellows 216 is secured bya weld 221. A bore, which communicates with the left end of the cavity218, threadingly receives a set screw 222. A compression spring 224 isinterposed between the left end of the bellows and the set screw to biasthe bellows in the direction of the spool. That portion of the cavity218 to the left of the annular abutment 220 is in communication with asignal conduit 226 which is adapted to receive a signal pressure, andthe other portion of the chamber 218 to the right of the annularabutment 220 is in communication with another signal conduit 228. Signalconduit 228 also communicates with port 208 to transmit the pressuretherein to the outboard face of land 194.

The pressure in signal 228 is maintained at a predetermined value abovethat in conduit 226 to maintain the spool in the position in which theactuator pistons are maintained in an equilibrium position, this beingthe illustration position. If desired, this differential pressurebetween the signal conduits 226 and 228 which maintains the spool in aneutral position may be varied by means of set screw 220 Assuming thatis desired to displace the track elements 26 and 28 to their minimumdisplacement positions, as shown in FIG. la, it is necessary to increasethe differential pressure between the signal conduits 226 and 228.Increasing the pressure in signal conduit 228 creates a force imbalanceon the spool and the bellows which shifts the spool to the left, therebydirecting high pressure into interconnecting conduit 184 via conduit154, port 204 and port 198. Simultaneously, the pressure in conduit 186is decreased as port 200, which is in communication therewith, nowcommunicates with port 206 via the annular space between lands 192 and194. Thus, the pressure in conduit 184 increases and the pressure inconduit 186 decreases, thereby producing a forced imbalance across theactuator pistons 174 of the actuator piston assemblies 34 and 36. Thisforced imbalance causes the pistons 174 of the respective actuatorassemblies to move outwardly, and thereby rotate the actuation ring 32in a clockwise direction. This rotation will continue until the spoolreturns to its original position, or the pistons 174 reach their limitsof travel within their respective cylinders.

Since the pressure between the surface of the rotor and the innerperipheries of the track elements is constantly urging the trackelements apart, the respective cam surfaces on the track elements remainin contact with the cam members on the actuation ring during rotation ofthe actuation ring. The track elements thus move outwardly from therotor to their minimum displacement positions. If it is desired that thetrack elements be stopped in their outward movement in an intermediateposition, the signal pressure in signal conduit 228 must be restored toits original value before the track elements have passed this position.It will be appreciated that the servo value illustrated provides onlyopen loop control, but that if desired a closed loop system can bereadily incorporated, as will be apprehended by those skilled in theart.

In order to displace the track elements from their minimum displacementpositions of FIG. 1a to their maximum displacement positions of FIG. 1,it is necessary to decrease the pressure in signal conduit 228 to causethe spool to shift to the right. Once the spool is shifted to the right,port 198 communicates with inlet pressure via branch conduit 212 andconduit 210, and hence interconnecting conduit 184 communicates withthis inlet pressure. Simultaneously, conduit 186 communicates withdischarge pressure via port 200, the annular space between lands 190 and192, port 204 and conduit 154. Thus, a force imbalance will be producedacross piston 174 which will produce a downward movement of the piston,thereby rotating the actuation ring 32 in a counterclockwise manner.This counterclockwise rotation, of course, displaces the cam blocksinwardly towards the rotor and increases the overall pump displacement.

If desired, filtered discharge flow may be employed to lubricate thebearings ofthe shaft 20. If this is the case, a suitable conduit, suchas conduit 230, may be employed to port lubricating flow to thebearings.

By way of general comment, the pump shown and described has minimalrotor bearing loads and controlled radial vane movement to minimize theinstability in dynamic loading of the vanes. Since the vane dynamics inthe illustrated pump are not severe, the pump is adapted to be driven ata high r.p.m.

It will be understood, of course, that while the form of the inventionshown and described herein constitutes the preferred embodiment of theinvention, it is not intended herein to illustrate all of the possibleand equivalent forms or ramifications of the invention which fall withinthe scope of the subjoined claims. It will also be understood that thewords used are words of description rather than of limitation, in thatvarious changes, such as changes in shape, relative size and arrangementof the parts, may be substituted without departing from the spirit andscope of the invention herein disclosed. For example, the vanes shownmay be replaced by step vanes, and the side plates thereof may beaccordingly modified such that inlet pressure discharge pressure, acombination of both, may be introduced into the vane step areas tocontrol the pressure loading between the vanes and the track elements toassure mechanical efficiency and reduced wear. Further, the illustratedservo valve could readily be replaced by other types of servo valveswell-known to those skilled in the art.

What is claimed is:

1. In a variable displacement vane pump, the combination comprising:

a housing having a pumping cavity therein and an inlet conduit incommunication with the cavity for supplying fluid thereto;

a cylindrical frame mounted within the cavity in spaced relationship tothe wall thereof;

a rotor mounted for rotation within the frame in coaxial relationshipthereto;

a plurality ofspaced radially movable vanes mounted on the periphery ofthe rotor;

a first track element having a radial inlet passage and a radialdischarge passage slideably mounted in the frame around the periphery ofthe rotor, the inner surface of the first track element providing acontoured track surface for contacting the tips of the vanes duringrotation of the rotor; v

a first cam surface on the outer periphery of the first track element;

a second track element, having a radial inlet passage and a radialdischarge passage, slideably mounted in the frame around the peripheryof the rotor such that the second track element engages and isdiametrically opposite the first trackelement, the inner surface of thesecond track element providing a contoured track surface for contactingthe tips ofthe vanes during rotation of the rotor;

a second cam surface on the outer periphery of the second track elementin diametrically opposed relationship to the first cam surface;

passage means in the frame to allow fluid from the pumping cavity toflow into the respective inlet passages in the track elements;

an actuation ring mounted upon the periphery of the frame in surroundingrelationship thereto, the periphery of the frame guiding the rotation ofthe actuation ring about an axis coaxial with the rotor;

first and second cam follower members mounted on the actuation ring indiametrically opposed relationship such that the first and second camfollower members respectively contact the first and second cam surfacesfor urging the track elements toward the rotor;

means to rotate the actuation ring such that the ring does not bearagainst the periphery of the frame; and

means to control the rotating means.

2. The combination of claim 1, further including:

balance assembly means to bear against the track elements for urging thetrack elements toward the rotor to facilitate rotation of the actuationring, and thereby, displacement of the track elements by the camfollower members.

3. The combination of claim 2, wherein the rotating means comprises:

first and second actuator assemblies mounted in the housing andrespectively connected to the actuation ring at diametrically opposedlocations thereon.

4. The combination of claim 3, wherein the controlling means comprises:

a servo valve mounted in the housing and adapted to supply pressurizedfluid to the actuator assemblies.

i to deliver a flow of filtered fluid thereto. 6. The combination ofclaim 5, further including:

means to fluidly interconnect the filter and the balance assembly meansto supply pressurized fluid thereto.

1. In a variable displacement vane pump, the combination comprising: ahousing having a pumping cavity therein and an inlet conduit incommunication with the cavity for supplying fluid thereto; a cylindricalframe mounted within the cavity in spaced relationship to the wallthereof; a rotor mounted for rotation within the frame in coaxialrelationship thereto; a plurality of spaced radially movable vanesmounted on the periphery of the rotor; a first track element having aradial inlet passage and a radial discharge passage slideably mounted inthe frame around the periphery of the rotor, the inner surface of thefirst track element providing a contoured track surface for contactingthe tips of the vanes during rotation of the rotor; a first cam surfaceon the outer periphery of the first track element; a second trackelement, having a radial inlet passage and a radial discharge passage,slideably mounted in the frame around the periphery of the rotor suchthat the second track element engages and is diametrically opposite thefirst track element, the inner surface of the second track elementproviding a contoured track surface for contacting the tips of the vanesdurIng rotation of the rotor; a second cam surface on the outerperiphery of the second track element in diametrically opposedrelationship to the first cam surface; passage means in the frame toallow fluid from the pumping cavity to flow into the respective inletpassages in the track elements; an actuation ring mounted upon theperiphery of the frame in surrounding relationship thereto, theperiphery of the frame guiding the rotation of the actuation ring aboutan axis coaxial with the rotor; first and second cam follower membersmounted on the actuation ring in diametrically opposed relationship suchthat the first and second cam follower members respectively contact thefirst and second cam surfaces for urging the track elements toward therotor; means to rotate the actuation ring such that the ring does notbear against the periphery of the frame; and means to control therotating means.
 2. The combination of claim 1, further including:balance assembly means to bear against the track elements for urging thetrack elements toward the rotor to facilitate rotation of the actuationring, and thereby, displacement of the track elements by the camfollower members.
 3. The combination of claim 2, wherein the rotatingmeans comprises: first and second actuator assemblies mounted in thehousing and respectively connected to the actuation ring atdiametrically opposed locations thereon.
 4. The combination of claim 3,wherein the controlling means comprises: a servo valve mounted in thehousing and adapted to supply pressurized fluid to the actuatorassemblies.
 5. The combination of claim 4, further including: adischarge conduit in the housing; means fluidly connecting the dischargeconduit with the radial discharge passages; a wash flow filter mountedin the discharge conduit; and means to fluidly interconnect the filterand the servo valve to deliver a flow of filtered fluid thereto.
 6. Thecombination of claim 5, further including: means to fluidly interconnectthe filter and the balance assembly means to supply pressurized fluidthereto.